1. FIELD OF THE INVENTION
This invention relates to a novel thermistor composition.
2. DESCRIPTION OF THE PRIOR ART
Compound metal oxides of spinel structure obtained by mixing at least two of oxides of Mn, Co, Ni, Fe, Al and Cu and firing the resulting mixture at 900.degree.-1,300.degree. C., thereby conducting a solid phase reaction are known as thermistor materials having a resistance of negative gradient to temperature and a large change in resistance by temperature, that is, a large thermistor constant. Said compound metal oxides are now used as materials for disc-form thermistor element and bead-form thermistor element owing to (i) their large thermistor constant and (ii) their easier production. Above all, compound metal oxides containing copper oxide has such an additional characteristic as (iii) a low specific resistance besides said characteristics (i) and (ii), and thus are used as materials for thermistor of low resistance. However, the compound metal oxides containing the copper oxide undergo a change in resistance with time of more than 10%, and thus have a poor stability, and cannot be used for temperature detection element and temperature compensation element with a high precision.
As thermistor materials containing oxide of Ru, compound metal oxides of pyrochlore structure (compound metal oxides of Cd, Bi, Nb and Ru) are known, but require firing at 1,200.degree. C. for 16 hours. (Japanese Laid-open Patent Application Specification No. 118,295/75).